> Including motion parameters should not remove any power from your signal
> of interest if movement isn’t correlated with the task.
I do not believe this is completely true as you do loose degrees of
freedom by including further regressors, which may hurt you especially
if you don't have too many scans to begin with. Also, your motion may be
correlated with the task but still be insignificant (i.1., .1 in "rest"
and .2 in "active" condition), which likely does not affect the signal
but is still correlated with the task and thus is being attributed true
signal. In other words, I do see drawbacks of routinely including motion
parameters independent of the amount of motion. But that is just me ;)
Marko Wilke (Dr.med./M.D.)
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Universitäts-Kinderklinik University Children's Hospital
Abt. III (Neuropädiatrie) Dept. III (Pediatric neurology)
Hoppe-Seyler-Str. 1, D - 72076 Tübingen
Tel.: (+49) 07071 29-83416 Fax: (+49) 07071 29-5473